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T–63 SECTION 17    STANDARDS APPLICABLE TO PULLEYS AND FLANGES Pulleys are components manufactured to close tolerances in order to achieve best performance and long belt life.  They are available in finished form or as bar stock which can be used for in-house manufacture of prototypes or smaller quantities. For an uninitiated observer, a pulley may appear simply as a component with some trapezoidal or curvilinear grooves.  In fact, the efficiency and integrity of a belt drive is closely attributed to the quality  of  pulleys  involved.    The  pulleys,  therefore,  should  be  supplied  by  qualified  and  licensed suppliers.  In case of HTD and GT drives, the suppliers must be licensed by the Gates Rubber Company.  Stock Drive Products is one of such licensed full line suppliers. To achieve the reproduction of the correct pulley profile, licensed hobs are used.  The following inspection and design aids are used as well: Master Profile:  A scaled line drawing of the ideal groove profile with tolerance bands plotted on dimensionally stable translucent material.  Suitable for groove inspection purposes on an optical comparator. Dimensional Profile Drawing:  A line drawing of the ideal groove profile with all arcs and radii defined.  Suitable for mold design. Digitized Points:  A series of X and Y coordinates defining the ideal groove profile.  Available in printed form or on a floppy disk.  Suitable for mold design. Table 25    Center Distance Tolerances inches mm inches Center Distance Tolerance Belt Length Up to   10 Over    10 To   15 Over    15 To   20 Over    20 To   30 Over    30 To   40 Over    40 To   50 Over    50 To   60 Over    60 To   70 Over    70 To   80 Over    80 To   90 Over    90 To 100 Over  100 To 110 Over  110 To 120 Up to   254 Over    254 To   381 Over    381 To   508 Over    508 To   762 Over    762 To 1016 Over  1016 To 1270 Over  1270 To 1524 Over  1524 To 1778 Over  1778 To 2032 Over  2032 To 2286 Over  2286 To 2540 Over  2540 To 2794 Over  2794 To 3048 .008 .009 .010 .012 .013 .015 .016 .017 .018 .019 .020 .021 .022 mm .20 .23 .25 .30 .33 .38 .41 .43 .46 .48 .51 .53 .56 Table 26    Overall Belt Thickness Dimensions inches mm Overall Thickness (ref.) Belt Type Belt Pitch MXL 40 D.P. XL 3 mm HTD 5 mm HTD 2 mm GT 3 mm GT 5 mm GT T2.5 T5 T10 .080" .0816" .200" 3 mm 5 mm 2 mm 3 mm 5 mm 2.5 mm 5 mm 10 mm .045 .045 .090 .095 .150 .060 .095 .150 .051 .087 .177   1.14   1.14   2.29   2.41   3.81   1.52   2.41   3.81 1.3 2.2 4.5 Table 27    Overall Belt Thickness Tolerances Standard Class 2 Class 1 0.015" 0.38 mm 0.010" 0.25 mm 0.005" 0.13 mm